The main cause of damage to church windows is excess damp and condensation. This can result from:
- exterior problems, such as defective gutters and drains
- interior problems like leaks, inadequate ventilation and heating systems causing high moisture levels
Structural defects such as inadequate support and failure of lead and copper ties can cause windows to crack or bulge. Cracks always require the attention of an accredited conservator.
Poorly-fired paint on stained glass windows can easily flake off.
Physical damage can result from vandalism and break-ins, or from high winds, falling trees or inappropriate cleaning.